Properties of ultra-high performance concrete and conventional concrete with coal bottom ash as aggregate replacement and nanoadditives: A review

Abstract

Ultra-high-performance concrete (UHPC) is a new type of concrete with improved features such as high strength, long service life, ductility, and toughness. UHPC's energy-intensive cement and quartz sand may make it unsustainable despite its engineering expertise. Thus, a UHPC that is energy efficient and environmentally benign should use less energy-intensive components and industrial wastes. This review consolidates and critically reviews the latest global research on coal bottom ash (CBA) as a fine aggregate replacement material and nano-calcium silicate hydrate (C-S-H) as concrete additives. Based on the critical evaluation, replacing aggregate with CBA up to 60% improves strength by 23%. Since high-quality natural sand is depleting and CBA output is increasing due to coal power plants, the concrete industry can use CBA as an aggregate. However, CBA as an aggregate substitute in UHPC has been scarcely reported. Besides, nanomaterial technologies like nano-C-S-H have also been proven to increase traditional concrete's strength by 33%. But, their impact on UHPC has yet to be fully explored. Thus, to develop UHPC with a lower carbon footprint and comparable or better performance to market-available UHPC, further research on CBA as aggregate replacement in UHPC with nano-C-S-H as an additive on mechanical durability and microstructure is needed.